This invention relates generally to a drive mechanism and more specifically to a drive mechanism having a clutch actuator assembly which responds to relative rotation between driving and driven members.
Known differential drive mechanisms having clutch assemblies which are actuated in response to relative rotation between driving and driven members are disclosed in U.S. Pat. No. 3,606,803 to Ottemann and in U.S. Pat. No. 3,845,672 to Goscenski. The differential disclosed in the Ottemann patent includes an actuator assembly having a pair of flyweights. A drive arrangement rotates the flyweights about a central axis of the actuator assembly to subject the flyweights to forces which vary as a function of the degree of relative rotation between the driving and driven members. Upon the occurrence of a predetermined degree of relative rotation, an active one of the flyweights will move outwardly under the influence of centrifugal force and engage a stop element to initiate operation of a clutch assembly to an engaged condition.
Although the aforementioned differential is generally satisfactory, lock-ups are occasionally missed. It was thought that a missed lock-up resulted from the fact that as the active one of the two flyweights moved outwardly, the inactive flyweight also moved outwardly and banged against the stop element to force it out of the way of the active flyweight with a resulting failure to lock-up. To substantiate this theory, the inactive flyweight was held in place and the stop surface on this flyweight was rounded off to render the inactive flyweight ineffective. Even in this condition, lock-ups were still occasionally missed. After considerable experimentation, it was determined that a stop surface located at or near the end of the flyweight would not move outwardly through a distance sufficient to engage the stop element. This defect could be remedied by increasing the angular distance through which the active flyweight pivoted outwardly as it moved from its retracted position to its extended position. However, space within known differential is very limited and increasing the angular distance through which the flyweight moves would result in interference with other components of the differential.